Hi,
I have found and issue with the Ekos mosaic tool than can be recreated with the Simulators. I generated a 1x2 mosaic job set, and a 2x1 set and compared the calculated RA and DEC using Stellarium.
The examples below show the issue. The 1x2 set has the correct 5% overlap. The 2x1 set has a 30% overlap. I've experience the same issue in the real world and found a 10% overlap resulted in images with a 60% overlap - but only when the short edge of the sensor overlaps. When the long edge overlaps things appear OK.

Right: